Dodecasyllable verse (Italian: dodecasillabo) is a line of verse with twelve syllables.
12 syllable lines are used in a variety of poetic traditions.
Dodecasyllabic meter was invented by Jacob of Serugh (d. 521), a Miaphysite bishop.
[1] With the so-called "political verse" (i.e. pentadecasyllable verse) it is the main metre of Byzantine poetry.
In an Anglo-Saxon and French context, the dodecasyllable is generally called the "alexandrine", after the French equivalent.